U.S. Pat. No. 4,138,426 discloses perfluorovinyl ether carboxylates of the formula ##STR1## wherein Y is --CO.sub.2 R, --CO.sub.2 H, --CO.sub.2 M or --CN, R is C.sub.1 to 6 alkyl, M is alkali metal, ammonium or quaternary ammonium and p is an integer 1 to 5.
Japanese Publication J5 No. 5015-410 discloses the thermal decomposition, at 230.degree.-400.degree. C., of metal salts of the formula ##STR2## wherein M is alkali metal, n is 0 or an integer 1 to 3, m is 0 or an integer 1 to 4 and n+m.noteq.0. The products are divinyl ethers of the formula ##STR3##
R. E. Banks, "Fluorocarbons and Their Derivatives", Elsevier (1970), page 22, discloses the solventless pyrolysis of perfluorovinyl carboxylic acid salts to perfluorodiolefins at 100.degree.-450.degree. C. and 0.01 mm Hg (1.3 Pa), for example, CF.sub.2 .dbd.CFCF.sub.2 CF.sub.2 CO.sub.2 Na to CF.sub.2 .dbd.CFCF.dbd.CF.sub.2, CO.sub.2 and NaF.
It is known that in the pyrolysis of acyl fluorides ##STR4## or the corresponding carboxylic acid salts ##STR5## to vinyl ethers (--OCF.dbd.CF.sub.2), CO.sub.2 and NaF, use of solvents such as tetraglyme is optional but may facilitate pyrolysis at lower temperatures. U.S. Pat. No. 3,114,778 discloses the pyrolysis of perfluorodicarboxylic acid salts to divinyl ethers, for example, ##STR6## CO.sub.2 and NaF, without solvent, at 170.degree.-250.degree. C. or, using solvent, at temperatures as low as 100.degree. C. U.S. Pat. No. 3,326,984 discloses the pyrolysis of an unsymmetrical perfluorodicarboxylic acid salt of the formula ##STR7## to the divinyl ether CF.sub.2 .dbd.CFOCF.dbd.CF.sub.2, without solvent, at 200.degree.-300.degree. C., or in an inert polar solvent such as tetraglyme, at 100.degree.-200.degree. C. In neither patent are different products or different product distributions, in the presence or absence of solvent, disclosed.
Hudlicky, "Chemistry of Organic Fluorine Compounds", MacMillan (1962), page 271, discloses the pyrolysis of salts of perfluoromonocarboxylic acids, both in the presence and absence of ethylene glycol as the solvent. For example, potassium perfluoropentanoate yields CF.sub.3 CF.dbd.CF--CF.sub.2 and CF.sub.3 CF.sub.2 CF.dbd.CF.sub.2 at 165.degree.-200.degree. C., but yields CF.sub.3 CF.sub.2 CF.sub.2 CF.sub.2 H at 170.degree.-190.degree. C. in the presence of ethylene glycol.
U.S. Pat. No. 3,847,978 discloses perfluoroketoacyl fluorides of the formula ##STR8## wherein n is 1 to 50 and X is COF or CO.sub.2 H. No ketovinyl ethers are disclosed.